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IUTAM Symposium on Topological Design Optimization of Structures, Machines and Materials: Status and Perspectives

作者： Wang, Michael Yu Wang, Shengyin Department of Automation and Computer-Aided Engineering Chinese University of Hong Kong Shatin NT Hong Kong

ISBN: (纸本)1402047290

This paper describes a parametric optimization technique for shape and topology optimization. The proposed method is a generalization of the classical method of level sets which are represented with discrete grids. In using radial basis functions (RBFs), the proposed formulation projects the geometric motion of the level sets of an implicit function onto its parametric representation. The resulting method provides a set of new capabilities for general shape and topology optimization, particularly treating it as a parameter problem with the RBF implicit models. Numerical examples are presented in the paper, suggesting the potential of the method. © 2006 Springer.

关键词： Numerical methods

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Dynamic balance control of multi-arm free-floating space robots

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International Journal of Advanced Robotic Systems 2005年第2期2卷 117-124页

作者： Huang, Panfeng Xu, Yangsheng Liang, Bin Department of Automation and Computer-Aided Engineering Chinese University of Hong Kong Hong Kong Hong Kong Shenzhen Space Technology Center Harbin Institute of Technology Shenzhen China

This paper investigates the problem of the dynamic balance control of multi-arm free-floating space robot during capturing an active object in close proximity. The position and orientation of space base will be affected during the operation of space manipulator because of the dynamics coupling between the manipulator and space base. This dynamics coupling is unique characteristics of space robot system. Such a disturbance will produce a serious impact between the manipulator hand and the object. To ensure reliable and precise operation, we propose to develop a space robot system consisting of two arms, with one arm (mission arm) for accomplishing the capture mission, and the other one (balance arm) compensating for the disturbance of the base. We present the coordinated control concept for balance of the attitude of the base using the balance arm. The mission arm can move along the given trajectory to approach and capture the target with no considering the disturbance from the coupling of the base. We establish a relationship between the motion of two arm that can realize the zeros reaction to the base. The simulation studies verified the validity and efficiency of the proposed control method.

关键词： Robots

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Kinematic control and obstacle avoidance for redundant manipulators using a recurrent neural network

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International Conference on Artificial Neural Networks, ICANN 2001

作者： Tang, Wai Sum Lam, Cherry Miu Ling Wang, Jun Department of Automation and Computer-Aided Engineering The Chinese University of Hong Kong Shatin New Territories Hong Kong

ISBN: (纸本)3540424865

In this paper, a recurrent neural network called the Lagrangian network is applied for obstacle avoidance in kinematically redundant manipulators. Conventional numerical methods implemented in digital computers for obstacle avoidance redundancy resolution calculation could only compute the solution in milliseconds while neural network realized by hardware could complete the computation in microseconds, which is more desirable in real-time control of manipulators. By giving the desired end-effector velocities and the obstacle location, the neural network could generate the joint velocity vector which drives the manipulator to avoid obstacles and tracks the desired end-effector trajectory simultaneously. Simulation results show that the neural network is capable of computing the redundancy resolution for obstacle avoidance. © Springer-Verlag Berlin Heidelberg 2001.

关键词： Recurrent neural networks

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Dynamic visual servoing of robots in uncalibrated environments

Dynamic visual servoing of robots in uncalibrated environmen...

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作者： Liu, Yun-Hui Wang, Hesheng Lam, Kinkwan Dept. of Automation and Computer Aided Engineering Chinese University of Hong Kong Shatin NT Hong Kong

ISBN: (纸本)0780389123

This paper presents a new adaptive controller for dynamic image-based visual servoing of a robot manipulator when the intrinsic and extrinsic parameters of the camera are not calibrated. To cope with nonlinear dependence of the image Jacobian on the unknown parameters, this controller employs a matrix called nonscaled image Jacobian which does not depend on the scale factors determined by the depths of feature points. By removing the scale factors, the camera parameters appear linearly in the close-loop dynamics so that a new algorithm, different from Slotine and Li's, is developed to estimate their values on-line. In the parameter adaptation, in addition to the regressor term, our algorithm also uses the errors between the real and estimated projections of the feature points on the image plane so as to guarantee the convergence of the estimated parameters to the real values up to a scale. A new Lyapunov function is introduced to prove asymptotic convergence of the image errors based on the robot dynamics. Experiments have been conducted to demonstrate the performance of the proposed controller. © 2005 IEEE.

关键词： Controllers

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Conceptual design of compliant mechanisms using level set method

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中国高等学校学术文摘·机械工程 2006年第2期1卷 131-145页

作者： Shi-kui CHEN Michael Yu WANG Computational Modeling and Design Laboratory Department of Automation and Computer-Aided EngineeringThe Chinese University of Hong KongShatinN.T.Hong KongChina

We propose a level set method-based framework for the conceptual design of compliant *** this method,the compliant mechanism design problem is recast as an infinite dimensional optimization problem,where the design variable is the geometric shape of the compliant mechanism and the goal is to find a suitable shape in the admissible design space so that the objective functional can reach a *** geometric shape of the compliant mechanism is represented as the zero level set of a one-higher dimensional level set function,and the dynamic variations of the shape are governed by the Hamilton-Jacobi partial differential *** application of level set methods endows the optimization process with the particular quality that topological changes of the boundary,such as merging or splitting,can be handled in a natural *** making a connection between the velocity field in the Hamilton-Jacobi partial differential equation with the shape gradient of the objective functional,we go further to transform the optimization problem into that of finding a steady-state solution of the partial differential *** the above-mentioned methodological issues,some numerical examples together with prototypes are presented to validate the performance of the method.

关键词： compliant mechanisms conceptual design level set methods shape gradient Hamilton- Jacobi PDE

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A recurrent neural network for non-smooth convex programming subject to linear equality and bound constraints

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13th International Conference on Neural Information Processing, ICONIP 2006

作者： Liu, Qingshan Wang, Jun Department of Automation and Computer-Aided Engineering Chinese University of Hong Kong Shatin New Territories Hong Kong

ISBN: (纸本)3540464816

In this paper, a recurrent neural network model is proposed for solving non-smooth convex programming problems, which is a natural extension of the previous neural networks. By using the non-smooth analysis and the theory of differential inclusions, the global convergence of the equilibrium is analyzed and proved. One simulation example shows the convergence of the presented neural network. © Springer-Verlag Berlin Heidelberg 2006.

关键词： Neural networks

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Asymptotic Solution for Coupled Heat and Mass Transfer During the Solidification of High Water Content Materials

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Transactions of Tianjin University 2010年第4期16卷 239-243页

作者：齐德瑄何凯杜如虚张义同 School of Mechanical Engineering Tianjin University Institute of Advanced Integration Technology Shenzhen Institute of Advanced Technology Chinese Academy of Sciences Department of Automation and Computer-Aided Engineering The Chinese University of Hong Kong

This paper focuses on obtaining an asymptotic solution for coupled heat and mass transfer problem during the solidification of high water content materials. It is found that a complicated function involved in governing equations can be approached by Taylor polynomials unlimitedly, which leads to the simplification of governing equations. The unknown functions involved in governing equations can then be approximated by Chebyshev polynomials. The coefficients of Chebyshev polynomials are determined and an asymptotic solution is obtained. With the asymptotic solution, the dehydration and freezing fronts of materials are evaluated easily, and are consistent with numerical results obtained by using an explicit finite difference method.

关键词： heat transfer mass transfer solidification asymptotic analysis

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The generalized Cahn-hilliard equations of multiphase transition for structural topology optimization

The generalized Cahn-hilliard equations of multiphase transi...

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DETC2005: ASME International Design engineering Technical Conferences and computers and Information in engineering Conference

作者： Zhou, Shiwei Wang, Michael Yu Department of Automation and Computer-Aided Engineering Chinese Univ. of Hong Kong Shatin NT Hong Kong

ISBN: (纸本)079184739X

This paper describes a generalized Cahn-Hilliard model for the topology optimization of multi-material structure. Unlike the traditional Cahn-Hilliard model applied to spinodal separation which only has bulk energy and interface energy, the generalized model couples the elastic energy into the total free energy. As a result, the morphology of the small phase domain during phase separation and grain coarsening process is not random islands and zigzag web-like objects but regular truss structure. Although disturbed by elastic energy, the Cahn-Hilliard system still keeps its two most important properties: energy dissipation and mass conservation. Therefore, it is unnecessary to compute the Lagrange multipliers for the volume constraints and make great effort to minimize the elastic energy for the optimization of structural topology. Furthermore, this model also makes the simple interpolation of stiffness tensors reasonable for multi-material structure in real simulation. To resolve these fourth-order nonlinear parabolic Cahn-Hilliard equations coupled with elastic energy, we developed a powerful mutigrid algorithm. Finally, we demonstrate that this new method is effective in optimizing the topology of multi-material structure through several 2-D examples. Copyright © 2005 by ASME.

关键词： Topology

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Modeling interactions of pulpal tissue with deformable tools in endodontic simulation

Modeling interactions of pulpal tissue with deformable tools...

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2005 IEEE International Conference on Robotics and automation

作者： Li, Min Liu, Yun-Hui Department of Automation and Computer-Aided Engineering Chinese University of Hong Kong Shatin N.T. Hong Kong

ISBN: (纸本)078038914X

Effective and efficient simulation of tissue-tool interactions is the key to a virtual endodontic training system. This paper presents a new force model for effectively simulating the interactions of the pulpal tissue with the endodontic tools. Based on the smoothed particle hydrodynamics (SPH) method, a particle-based pulpal tissue model is proposed, which takes into account characteristics of the tissue and constraints associated with both the tissue and current haptic devices. The stability, accuracy and speed of the proposed model are guaranteed by applying suitable smoothing kernels to calculate different forces applied to the pulpal tissue. Furthermore, a finite element model is used to model the deformation and dynamics of the endodontic tools. We also derive several boundary constraints associated with interactions of the pulpal tissue with the endodontic tools. With this force model, the virtual system can provide the convincing sense of touch of endodontic procedures in real time using current high fidelity haptic devices. © 2005 IEEE.

关键词： Tissue

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A game-theoretic adaptive categorization mechanism for ART-type networks

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International Conference on Artificial Neural Networks, ICANN 2001

作者： Fung, Wai-Keung Liu, Yun-Hui Department of Automation and Computer Aided Engineering The Chinese University of Hong Kong Shatin N.T Hong Kong

ISBN: (纸本)3540424865

A game-theoretic formulation of adaptive categorization mechanism for ART-type networks is proposed in this paper. We have derived the game-theoretic model ΓAC for competitive processes of categorization of ART-type networks and an update rule for vigilance parameters using the concept of learning automata. Numbers of clusters generated by ART adaptive categorization are similar regardless of the initial vigilance parameters ρ assigned to the ART networks as demonstrated in the experiments provided. The proposed ART adaptive categorization mechanism can thus avoid the problem of choosing suitable vigilance parameter a priori for pattern categorization. © Springer-Verlag Berlin Heidelberg 2001.

关键词： Game theory

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